Field of the Invention
The present invention relates to an economical gas separation membrane module for use in the separation of gases from a reactive feed gas that includes sealing features that exhibit greater resistance to leaks.
Related Art
Many gas separation membrane modules include a plurality of hollow fibers arranged in a bundle where at least one end of the bundle is embedded in a tubesheet and the bundle is installed within a pressure vessel. The feed gas may contact the membrane bundle from the shell side (i.e., the outer surfaces of the hollow fibers) or from the tube/bore side of the hollow fibers (i.e., the inner surfaces of the hollow fibers).
When fed from the bore side, gas components preferentially permeate through the fiber wall from the fiber bores to spaces outside the fibers. These preferentially permeated gases are withdrawn from the shell side as a permeate stream through a permeate port. The residue stream, which is depleted in these preferentially permeating components, is withdrawn from a residue port.
Typically for higher pressure operation, in contrast, the feed is brought into contact with the hollow fiber bundle from the shell side. The feed flow path typically has an outside-in orientation, although the reverse orientation is also possible. The preferentially permeating gas components pass through the walls of the hollow fibers and into the bores of the hollow fibers. The preferentially permeating gas components are withdrawn from the permeate port as a permeate stream and the depleted feed gas (depleted in the preferentially permeating gas components) is withdrawn from the residue port as a residue stream.
While the above-described membrane modules are ordinarily satisfactory for many types of feed gases, they can potentially be susceptible to leaks (i.e., feed gas leak into permeate gas, feed gas leak into residue gas, or feed gas leak outside the module) when the module is put into acid gas service. By acid gas service, we mean that the feed gas is corrosive and contains acid gases such as H2S and CO2, such as sour natural gas. This susceptibility to leaks is exacerbated by relatively high levels of acid gases in the feed gas, especially H2S. For example, some have reported H2S concentrations for very sour or ultra-sour natural gas that are in double digit percentages and may reach even as high as 75% vol.
Therefore, there is a need in the art of membrane-based gas separation for gas separation membrane modules that are not as susceptible to leaks.